Artificial cellulosic structure



7; H H. LEVIN 2 ,141,396

ARTIFICIAL GELLULOSIC STRUCTURE Filed May 14, 1956 Harry HL-ew'z? INVENTOR.

A TTORNE Y Patented Dec. 27, 1938" PATENT OFFICE 2,141,396 ARTIFICIAL CELLULOSIC STRUCTURE Harry B. Levin, New York, N. Y., assignor, by

mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware Application May 14, 1936, Serial No. 79,811 2.0laims. -((21. 1399-4126) This invention relates to fabrics constructed from regenerated cellulose threads, and. more particularly it relates to improved laundry or clothes pressing fabrics comprising regenerated cellulose threads having a high wet and. dry

5 tenacity, a comparatively low percentage elongation, and having a high hot strength.

In laundry and clothes pressing machines, the pressing elements are covered with fabric which is ordinarily heated to temperatures. of 250-330" F. by internal heating means, or through which steam is passed, to suitably smooth or crease the laundry or clothes placed therein.

Heretofore, fabrics for laundry presses have been universally made from cotton thread. Due to the high temperatures to which the fabrics 'aresubjected during the pressing operation, cotton soon scorches, loses its strength and must ordinarily be replaced within a comparatively short period of time. In some cases, even though 30 the cotton cloth is not completely worn out after a short period of use, the scorched lint on the surface of the fabric has been found to stain the laundry to such an extent that the fabric must be replaced forthis reason. H

35 Cotton fabric also hasa great aiiinity for starch. Heavily starched laundry has been found to damage cotton pressing fabric to such an extent that it is sometimes replaced with wool fabric which has a much lower amnity for starch than cotton. Wool fabric, on the other hand, hasstill less resistance than cotton to deterioration at elevated temperatures.

Many attempts have been made, prior to this invention, to find a satisfactory material which will overcome the disadvantages of cotton and wool in the construction of laundry pressing cloth. It has been suggested to use laundry pressing fabrics made from ordinary standard rayon, however standard rayon was found to be entirely unsuitable for this purpose due to its low wet strength, high elongation, and tendency to pucker at high temperatures in the presence of moisture. The use of asbestos fabric for pressing cloths has been suggested, however asbestos fabric isobjectionable in view of its rough tex-' ture and tendency to impart a rough flnish\togoods'being pressed.

It is therefore=an object of the present invention to provide an impizoved laundry pressing fabric. a

It is another object of this invention to provide a laundry pressing fabric\comprising regenerated cellulose threads which have satisfactory tenacity, elongation and hot strength characteristlcs.

It is a further object of this invention to provide a laundry pressing fabric comprising regenerated cellulose threads having a high wet and dry tenacity, a comparatively low percentage elongation, which will maintain its strength to a substantial degree at elevated temperatures, and 5 which will satisfactorily resist deterioration and distortion at elevated temperatures in the presence of moisture.

Other objects of the invention will appear hereinafter.

Reference is made to the accompanying illustration showing generally a piece of laundry pressing fabric I. This illustration shows a magnified sketch 2 which clearly discloses the weave of the fabric in which both the warp threads 4 and the filling threads 3 are constructed of regenerated cellulose threads having suitable tenacity, elongation and hot strength, as hereinafter specifically set forth.

The defects and objectionable characteristics of cotton fabric when used as a laundry or clothes pressing fabric have long been known in the art. After due investigation it was found that the causes of these defects and objectionable characteristics of cotton were primarily due to its discontinuous filament structure, and its low hot strength. The discontinuous filament structure of cotton thread will cause it to have innumerable projecting fiber ends or lint on its surface. These fiber ends will become brittle and discolored or scorched after a short period of use at an elevated temperature. The brittle, discolored fiber ends are broken off and pressed into the clothes or laundry and discolor the latter.

The low hot strength of cotton fabric, by which is meant the decreased tenacity of the fabric 'at elevated temperatures, causes the same to fall after a surprisingly short period of use at the elevated temperatures necessarily employed. Cotton fabric, when subjected to a temperature of 40 250" E, has been found to have a dry tenacity which is only to of the dry tenacity thereof at room temperature.

It has been found that regenerated-cellulose thread'can be produced which will have a com- 45 paratively high wet and dry tenacity, a comparatively low. elongation, with a continuous filament structure and a high hot strength which is admirably suited for use in pressing fabric.

In accordance with the preferred embodiment of 50 the present invention the rayon used in pressing fabric shall have 'a dry tenacity at room temperature F.) of at least 2.5 grams per denier, for example 2.7, 2.8, 2.9, 3.0 grams per denier or more, a wet tenacity at room temperature of at'least 1.5 grams perdenier, for example, 1.7 grams per denier, 1.9 grams per denier or more, a percentage elongation not in excess of 12%, such as, for example, 10%, 8% or less, a hot strength of 250 F. o'f-at least 80%, such as, for,

example, 85%, 87% or more, of its strength at room temperature.

High tenacity thread, adaptable for use in the present invention, may be obtained by the viscose process, as described in the United States patent application of Harold H. Parker, Serial No. 676,463, filed June 19, 1933.

Briefly, the process comprises shred n purl fied linters of wood pulp which have been saturated with a strong caustic soda solution, aging the shredded soda-cellulose crumbs, reacting with carbon disulphide to form cellulose xanthate, dissolving this in an alkaline solution, forcing the resultant viscose solution through a filter and spinneret through an acid precipitating bath, and

finally collecting and spinning the filaments regenerated in the acid bath.

The following examples illustrate types of high tenacity rayon fabrics suitable for use in the manufacture of laundry pressing cloth in accordance with the present invention.

Example I 275 denier-120 filament regenerated cellulose thread produced by the viscose process, twisted to 7 turns per inch, and having a dry tenacity of 3.0 grams per denier, an elongation of 10%, and

a hot strength at 250 F. of 2.5 grams per denier or about 85% of its strength at room temperature, is used as both warp and filling thread in the manufacture of a fabric. The warp comprises 92 threads to the inch, and the filling comprises 76 threads to the inch, the fabric being 56 inches wide and of any desired length. The fabric thus formed weighs 0.58 pound per linear yard, having the said width of 56 inches.

Example II wide and of any desired length. The fabric thus formed weighs 1.05 pounds per linear yard, having the said width of 100 inches.

Example III 500 denier-200 filament regenerated cellulose thread produced by the viscose process, twisted to 3 turns per inch, and having a dry tenacity of 2.5 grams per denier, an elongation of 12%, and

a hot strength at 250 F. of 85% of its strength 7 at room temperature, is used as both warp and filling thread in the manufacture of afabric. The warp comprises 43 threads to the inch, and

the filling comprises 42 threads to the inch, the

fabric being 72 inches wide and of any desired length. The fabric thus formed weighs 0.69

pound'per linear yard, having the said width of '72 inches.

Rayon fabrics, constructed in accordance with the above examples, when applied to the pressing elements of cloth or laundry pressing machines are found to be more satisfactory and last for a longer period of time than similar fabric produced from cotton thread.

In testing high tenacity, low elongation rayon fabrics of the type described in the above examples and similarly constructed cotton fabrics under identical conditions, on pressing machines having a temperature of 325 F., the cotton fabric was found to fail completely after one weeksservice, while the said rayon fabric, after four weeks of service, was still in excellent condition.

In a specific test, performed for comparison between cotton fabric and high tenacity, low elongation, high hot strength rayon fabric of the type hereinabove described, each fabric was sub- .mitted to actual and identical working conditions on a fiat work chest type ironer. The said rayon fabric was found to be serviceable as a laundry pressing fabricfor four weeks, whereas the said cotton fabric was serviceable only for one week.

In another test between the two above mentioned, fabrics under actual identical working conditions on a buck type press it was found that the said rayon fabric gave service for 143 hours and the said cotton fabric gave service for only 32 hours.

When submitted to the high temperatures present in pressing machines of the type hereinabove set forth, cotton fabric scorches very rapidly. The cotton thread being produced from short length cotton fibers will naturally contain innumerable projecting fibers on the surface of the fabric. These projecting fibers will, after they have been scorched, become brittle and break from the fabric to be picked up by the laundry which is being pressed with the result that the surface of the laundry will be objectionably stained.

The high tenacity, low elongation, high hot strength rayon fabric constructed in accordance with the principles of the present invention shows only a slight discoloration after a long period of time, and due to the continuous filament structure of rayon threads, will have no projecting fibers. As a consequence it will not stain laundry even after having been in service for a. considerable length of time.

Furthermore, due to the smooth nature and the continuous filamentary structure of rayon threads, laundry presses covered with the high tenacity rayon fabric will give a much better finish to the laundry being pressed.

Laundry pressing fabrics constructed of rayon of the type above set forth have been found to have less aflinity for starch than the cotton fabrics which have previously been used, and consequently can be used more advantageously than cotton fabrics in pressing starched laundry.

Elongation (unless otherwise qualified), as used throughout the specification, means percentage elongation of the dry thread at the breaking point, when tested at room temperature as described hereinafter.

Tenacity or its equivalent (unless otherwise qualified), as used throughout the specification and claims, signifies the maximum load which can be put on the wet or dry thread (as specified) at room temperature according to the test described hereinafter.

Both tenacity and elongation of high tenacity rayon are determinedby the following test:

The thread is reeled under uniform tension to 450 meter skeins; these skeins are conditioned for three hours in an atmosphere maintained at 60% relative humidity and 75 F.; the skeins are then weighed to determine the denier which is defined as the weight in grams of 9000 meters.

The tests for determining tenacity and elongation are made on a Suter single strand strength and elasticity tester with an oil plunger controlled pull. The rate of fall of the plunger is 1 foot per minute, and the distance between the clamps is adjusted for an 18" length of yarn. In making the dry test, five single strands from each of the above skeins are tested separately. These are clamped in the tester and stretched until the yarn breaks. Both the breaking load in grams and the per cent elongation may be read directly from scales on the machine.

G per denier are obtained by dividing the scale reading in grams by the denier of the thre.

The average of 50 dry breaks on threads selected at random is considered to be the tensile strength for any given 100 pound lot ofv yarn.

Where methods of testing other than those specifically referred to herein are used, difiere'nt numerical results y be obtained, but the relative improvement over the prior art will be of the same order, regardless of the method of testing Since the invention is capable of considerable modification and variation from the details given above, any change which conforms to the spirit oil the invention is intended to be included in the a I claim:

1. A non-puckering, heat-resisting, substantially lint-less clothes pressing fabric for use in a *clothes pressing machine of the type in which pressing is carried out at a temperature as high as 250 F. and in the presence of high humidities, said fabric consisting largely of continuous filament rayon threads having a drytenacity at room temperature of at least 2.5 grams per denier and a percentage elongation not in excess of 12%, said threads having a denier of from about 275 to about 500, said fabric containing about 42 to about 92 threads per inch in both the warp and the filling.

2. A non-puckering, heat-resisting, substan tially lint-less clothes pressing fabric for use in a clothes pressing machine of the type in which pressing is carried out at a temperature as high as'250 F. and in the presence of high humidities, said fabric consisting largely of continuous regenerated cellulose rayon threads having a dry tenacity at room temperature of at least 2.5 grams per denier and a percentage elongation not in excess of 12%, said threads having a denier of from about 275 to about 500, said fabric containing about 42 to about 92 threads per inch in both the warp and the filling. 

